Measurement of filtration efficiencies of healthcare and consumer materials using modified respirator fit tester setup.

During the current SARS-CoV-2 pandemic there is unprecedented demand for personal protective equipment (PPE), especially N95 respirators and surgical masks. The ability of SARS-CoV-2 to be transmitted via respiratory droplets from asymptomatic individuals has necessitated increased usage of both N95 respirators in the healthcare setting and masks (both surgical and homemade) in public spaces. These precautions rely on two fundamental principles of transmission prevention: particle filtration and droplet containment. The former is the focus of NIOSH N95 testing guidelines, and the latter is an FDA guideline for respirators and surgical masks. While studies have investigated droplet containment to provide guidance for homemade mask production, limited work has been done to characterize the filtration efficiency (FE) of materials used in home mask making. In this work, we demonstrate the low-cost (<$300) conversion of standard equipment used to fit-test respirators in hospital and industrial settings into a setup that measures quantitative FEs of materials based on NIOSH N95 guidelines, and subsequently measure FEs of materials found in healthcare and consumer spaces. These materials demonstrate significant variability in filtration characteristics, even for visually similar materials. We demonstrate a FE of 96.49% and pressure drop of 25.4 mmH20 for a double-layer of sterilization wrap used in surgical suites and a FE of 90.37% for a combination of consumer-grade materials. The excellent filtration characteristics of the former demonstrate potential utility for emergent situations when N95 respirators are not available, while those of the latter demonstrate that a high FE can be achieved using publicly available materials.

Thermal response to firefighting activities in residential structure fires: impact of job assignment and suppression tactic.

Firefighters' thermal burden is generally attributed to high heat loads from the fire and metabolic heat generation, which may vary between job assignments and suppression tactic employed. Utilising a full-sized residential structure, firefighters were deployed in six job assignments utilising two attack tactics (1. Water applied from the interior, or 2. Exterior water application before transitioning to the interior). Environmental temperatures decreased after water application, but more rapidly with transitional attack. Local ambient temperatures for inside operation firefighters were higher than other positions (average ~10-30 °C). Rapid elevations in skin temperature were found for all job assignments other than outside command. Neck skin temperatures for inside attack firefighters were ~0.5 °C lower when the transitional tactic was employed. Significantly higher core temperatures were measured for the outside ventilation and overhaul positions than the inside positions (~0.6-0.9 °C). Firefighters working at all fireground positions must be monitored and relieved based on intensity and duration. Practitioner Summary: Testing was done to characterise the thermal burden experienced by firefighters in different job assignments who responded to controlled residential fires (with typical furnishings) using two tactics. Ambient, skin and core temperatures varied based on job assignment and tactic employed, with rapid elevations in core temperature in many roles.

Questionable effectiveness of the QuantiFERON-TB Gold Test (Cellestis) as a screening tool in healthcare workers.

OBJECTIVE: The Center for Disease Control and Prevention recommends the use of QuantiFERON TB Gold test (QFTG; Cellestis) in all situations where the tuberculin skin test (TST) is used. In November 2007, our institution replaced its screening-tool TST with the QFTG in-tube assay (QFT-GIT) for annual screening of latent tuberculosis infection among healthcare workers (HCWs). This study evaluated the effectiveness of QFT-GIT test as screening tool in HCWs at our institution. METHODS: This retrospective study reviewed medical records of all HCWs who underwent screening with QFT-GIT from January 2008 through December 2008. RESULTS: Among the 6,530 HCWs screened with QFT-GIT from January through December 2008, 287 had a positive test result. Of the 287, 123 had positive TST results in the past, meaning that 164 HCWs had newly diagnosed latent tuberculosis infection by QFT-GIT. Of the 164 HCWs, 135 were retested by QFT-GIT and were simultaneously tested with TST within 4 weeks after the initial QFT-GIT. Of these 135 HCWs, 66 reverted to negative results and results remained positive for 69 with QFT-GIT. Only 2 HCWs had a positive TST result. CONCLUSIONS: The disagreement between QFT-GIT and TST results and the high reversion rate with QFT-GIT raise concerns about the effectiveness of QFT-GIT as a sole screening test in HCWs.